import java.util.LinkedList;
import java.util.Queue;

public class Mystack2 {
    private Queue<Integer> qu1;
    private Queue<Integer> qu2;

    public Mystack2() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }
    public void push(int x){
        if (!qu1.isEmpty()){
            qu1.offer(x);
        }else if (!qu2.isEmpty()){
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
    }
    public int pop(){
        if (empty()){
            return -1;
        }
        if (!qu1.isEmpty()){
            int size = qu1.size();
            for (int i = 0;i < size-1;i++){
                int val = qu1.poll();
                qu2.offer(val);
            }
            return qu1.poll();
        }else {
            int size = qu2.size();
            for (int i = 0;i < size-1;i++){
                int val = qu2.poll();
                qu1.offer(val);
            }
            return qu2.poll();
        }
    }
    public boolean empty(){
        return qu1.isEmpty() && qu2.isEmpty();
    }
}
